There are genuine GM switches and aftermarket switches that look nearly like yours. I don't know what you mean by adaptor? If you are speaking of how to wire, looks like the wire fits in the barrel and you crimp it or solder it? Mike has given you the "how to wire" and explanation of circuit. You may want to buy new ones, They have the barrel end or spade end. Don't forget to fuse it.

From the Stovebolt tip section:

http://www.stovebolt.com/techtips/interior/dome%20light/index.html


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